sort objects in outliner case-insensitive
I think there's no need in addon for the thing like that.

The software put a new object name with an upper case because of python script in the source code that define an objects' (for example cube) name with upper case. So the solutions are:


Name your objects with a capital letter
Rewrite source files. I mean put cube instead of Cube in every file where it is. But it's time consuming


PS

You can create new objects on the separate layer with enabled option "visible layers" in outliner